To increase the areal storage density of a magnetic recording device, the recording layer thereof may be provided with smaller and smaller individual magnetic grains. This reduction in grain size soon reaches a “superparamagnetic limit,” at which point the magnetic grains become thermally unstable and incapable of maintaining their magnetization. The thermal stability of the magnetic grains can be increased by increasing the magnetic anisotropy thereof (e.g., by utilizing materials with higher anisotropic constants). Increasing the magnetic anisotropy of the magnetic grains, however, increases their coercivity and therefore requires a stronger magnetic field to change the magnetic orientation of the grains (e.g., in a write operation).
Energy assisted magnetic recording (EAMR) is used to address this challenge. In an EAMR system, a small spot where data is to be written is locally heated to reduce the coercivity of the magnetic grains therein for the duration of the write operation, thereby allowing materials with increased magnetic anisotropy to be used, and greater areal storage density to be exploited.
Several approaches to providing a heat source in an EAMR system have been tried. One approach involves fabricating a laser diode inside the slider of a magnetic recording head. This approach requires a semiconducting wafer or some semiconducting materials (e.g., GaAs and AlGaAs) for fabricating the slider, which would complicate the magnetic head fabrication process and would greatly increase the cost of the slider. Another approach involves mounting the laser remote from the head and carrying the laser beam to the slider through an optical fiber. This approach might require integrating and aligning multiple optical fibers and other optical components into a laser-slider assembly, which would also increase the cost and time required to produce the magnetic recording head.